There are two large dams on the Union River. The largest is approximately 72 feet high. There are no FERC license requirements for permanent upstream or effectiveness testing for current downstream passage. The current dam owners, Black Bear Hydropower (formally Pennsylvania Power and Light) are not required to provide permanent upstream passage for diadromous or resident fish species. Since 1996, the harvester has artificially propagated the alewife run. The harvester currently stocks 90,000 alewives upstream into the Graham Lake. The water storage dam expanded the size of Graham Lake to 7,865 acres. Once the harvester attains the stocking goal, the management plan permits the municipality to harvest all remaining river herring coming up the fishway, which ends in the hydropower station parking lot. The main downstream passage for all fish is through the hydropower turbines, though there is a downstream passage available. This results in high mortality for both adult and juvenile river herring. The management plan has achieved the target escapement developed for this system each year during the past 20-year period solely through the efforts of the harvester. The small headpond created by the actual hydropower dam is typically not stocked with the additional 14,000 river herring due to its limited size and location adjacent to the hydropower turbines. The hydropower facility is a peaking operation where water is stored during the night and passed though the turbines during the day when power demand is highest. Spill conditions exist for only three weeks during the early spring ice melt. During the remainder of the year, there is no spill over the dam except during high water resulting from an extreme rain event. For several years the numbers alewife stocked above the hydropower dam occurred as the result of the harvesters trucking as many fish as possible during the closed fishing days. Prior to the 1980s the state resource agencies transported fish above the hydropower facility to initiate a river herring run. These stockings resulted in returns as high as 1.8 million returning alewives in the mid-1980s.
There is no spawning below the dam for either species. The Union River is tidal to the base of the dam and provides little riverine habitat for any anadromous fish species. Atlantic salmon caught in the trap are trucked upstream. There are several ponds in the watershed that could support river herring but alewife reintroductions are not permitted by the Department of Inland Fisheries and Wildlife because of perceived conflicts with sport fish species, rainbow smelt, or hatchery operations.